Mara (Alice Englert) has grown up in the rural church where her widowed Bible-thumping father, Lemuel (Walton Goggins), is the preacher. A typical ceremony finds the menfolk of the congregation so moved by the Holy Spirit that they reach into a wooden box and withdraw hissing rattlesnakes.

They’re fulfilling a Biblical prophecy that if they are truly saved, they can handle poisonous serpents and God will protect them.

The snake handling doesn’t freak out Mara. What does give her sleepless nights is the baby growing inside her. It’s the result of an affair with her childhood friend Augie (Thomas Mann), the son of one of the church’s most steadfast members (Olivia Colman).

But Augie has been drifting from the religious community. He’s talking about moving away to find work and, presumably, himself.

Which leaves Mara…where? Her father has approved her betrothal to Garrett (Lewis Pullman), who has no misgivings about the faith; but how’s that going to play when Garrett learns of her condition?

Watching a familiar actor utterly lose him/herself in a role is one of the deep pleasures of moviegoing.

Liev Schreiber makes that transformation in “Chuck.” But then so do Naomi Watts (a.k.a. Mrs. Schreiber), Elizabeth Moss, Ron Perlman and Jim Gaffigan.

The subject of director Philippe Falardeau’s bracing little film (the screenplay is credited to Jeff Feuerzeig, Jerry Stahl, Michael Cristofer and Schreiber) is Chuck Wepner, the New Jersey club fighter known affectionately/sardonically as the “Bayonne Bleeder” for his willingness to be beaten to a pulp. (In fact, “Chuck’s” original title was “The Bleeder.” Wish they’d stuck with it.)

In 1975 the virtually unknown Wepner got a crack at taking away Muhammad Ali’s heavyweight belt in a bout conceived and advertised by promoter Don King as a blatant racial confrontation.

Wepner didn’t win, but he lasted for more than 14 bloody rounds against the world’s best, sending the champ to the mat once and losing by a TKO with only 19 seconds left in the fight.

Out in Hollywood a struggling actor named Sylvester Stallone was so inspired by Wepner’s David-and-Goliath story that he wrote a screenplay called “Rocky.”

“Chuck” isn’t really a boxing film. Rather, it is simultaneously a fact-based yarn about the ever-widening fallout from the Ali-Wepner fight and a character study of a Palooka whose a brief brush with fame went straight to his head.

Schreiber’s Chuck, who narrates his story, is by most accounts a pretty average guy. He worked as a nightclub bouncer and as a debt collector for a loan shark, though his heart wasn’t in it. (“I was never good at roughing guys up. Too nice.”)

His wife Phyllis (Moss) is the family breadwinner, thanks to her gig with the U.S. Post Office. Chuck shows his appreciation by writing heartfelt doggerel about her virtues.

Eventually an admirer lands Chuck a liquor distributorship. It’s an OK living, but it provides way too many opportunities to hang around bars and pick up other women. (It also provides an opportunity for a soundtrack filled with disco hits.)

The Ali fight provides Chuck with bragging rights and celebrity status. Once “Rocky” becomes an Oscar-winning phenomenon, everyone assumes he must have sold his story to the movies for big bucks. In fact, Chuck didn’t earn a cent off the film.